Pyrite deformation textures in the deposits of the Küre mining district (Kastamonu-Turkey)
Küçük Resim Yok
Tarih
2002
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Küre volkanojenik masif sülfid yatakları Pontid Kuşağının batısındaki Kastamonu bölgesinde yer alır. Yataklar, ofiyolitlerle ilişkili Liyas öncesi yaşlı bazaltik seriler içinde bulunur. Bu yataklarda yapılan cevher mikroskopisi çalışmaları piritlerin deformasyon etkileri altında kaldığını ve dolayısıyla bir seri deformasyon ve geç-deformasyon dokusunun oluştuğunu göstermektedir. Bu dokular ardışık iki aşamanın ürünleri olan kataklastik, ikincil tane gelişimi ve çatlak dolgu dokularıdır. Kataklastik doku deformasyon evresinde oluşurken ikincil tane gelişimi ve çatlak dolgu dokusu ise geç-deformasyon aşamalarında oluşmuştur. Kataklastik doku daha çok iri taneli pirit kümelerinde daha baskın bir dokudur. Tek tük taneler üzerinde kataklastik doku ya hiç gelişmemiş ya da çok azdır, ikincil tane gelişim dokusu piritin rekristalizasyonuyla oluşurken çatlak dolgu dokusu piritlerdeki çatlakların kalkopirit ile doldurulmasıyla oluşmuştur. Kataklastik dokunun, düşük dereceli metamorfik koşullarda ve/veya yeşilşist fasiyesi koşullarına benzer olarak yaklaşık 400C-500C sıcaklık ve 1 kb-3 kb basınç koşullarında oluştuğu düşünülmektedir, ikincil tane gelişim dokusu ise üst yeşilşist/amfibolit fasiyesleri için tipik olan 500°C-550°C sıcaklık ve 0.69 kb-1.7 kb basınç koşullarında baskın hale gelmektedir. Çatlak dolgu dokuları ise 600°C'den daha yüksek sıcaklık ve 500 bar'dan daha düşük basınç koşullarında oluşmuş olmalıdır. Bu sıcaklık değerleri bu tür bir deformasyonda ulaşılabilecek en yüksek sıcaklıklara karşılık gelmekte olup gerçek değerler daha düşük olmalıdır. Küre masif sülfid yatağında bu dokulardan en az ikisinin veya tümümün aynı örnekte gözleniyor olması bu yatakların oluştuktan sonra ilerleyen bir deformasyon etkisiyle yeşilşist-amfibolit fasiyeslerinde deforme olduklarının bir göstergesi olarak değerlendirilebilir.
The Küre volcanogenic massive sulfide deposits lie within the Kastamonu province in the western part of the Pontide tectonic belt of Turkey, and are hosted by ophiolite-related pre-Liassic basaltic sequences. Mineralogical studies of the pyritic massive sulfide deposits of the Küre mining district have shown that the sulfide assemblages, particularly pyrite, have undergone a history of deformation and metamorphism. The Küre volcanogenic massive sulfide deposits show a range of macroscopic and microscopic textures, which are also observed in metamorphosed VMS deposits elsewhere. These textures are cataclastic, annealing and fracture-filling textures which developed in two successive stages; cataclastic texture predominated during main deformational stages, whereas annealing and fracture filling textures predominate during late-deformational stages. Cataclastic texture predominantes in polycrystalline and coarser-grained pyrite. Little or no cataclastic texture is observed in single, fine-grained pyrite crystals. Annealing is characterized by recrystallization of pyrite, while fracture filling is characterized by replacement and infilling of cataclastic fractures in pyrite grains by chalcopyrite. Cataclastic deformation texture is likely to have formed at about 400°C to 500°C and at 1 kb to 3 kb pressures, typical of low-grade and/or greenschist-facies metamorphic conditions, whereas annealing textures dominate at temperatures over 500°C-550°C and at 0.69 kb to 1.7 kb pressures, typical of uppergreenschist-/amphibolite-facies metamorphism. Fracture-filling textures, however, should have formed at less than 600°C and less than 500 bars. These temperatures indicate the maximum temperatures that could be reached in such deformation processes. The actual temperatures should be less than these values. The coexistence of at least two or all of the textures in at least one sample from the Küre massive sulfide deposits may indicate that the ore bodies were subjected to a progressive deformation/metamorphic event, ranging from greenschist- to upper greenschist- or even to amphibolite-facies conditions. The imbricate thrust fault and plunging anticlinal/synclinal structures between the Akgöl Formation and the Küre Ophiolite, which postdate the formation of the massive sulfide deposits, may have been the driving mechanism for the development of deformational- and late-deformational textures in the district. Also, it is proposed that many of the copper-bearing minerals may have been remobilized from their original settings to nearby fractures during late deformational stages; this is a possible explanation of why the massive ore tends to be confined to fault planes rather than within altered basalt sequences.
The Küre volcanogenic massive sulfide deposits lie within the Kastamonu province in the western part of the Pontide tectonic belt of Turkey, and are hosted by ophiolite-related pre-Liassic basaltic sequences. Mineralogical studies of the pyritic massive sulfide deposits of the Küre mining district have shown that the sulfide assemblages, particularly pyrite, have undergone a history of deformation and metamorphism. The Küre volcanogenic massive sulfide deposits show a range of macroscopic and microscopic textures, which are also observed in metamorphosed VMS deposits elsewhere. These textures are cataclastic, annealing and fracture-filling textures which developed in two successive stages; cataclastic texture predominated during main deformational stages, whereas annealing and fracture filling textures predominate during late-deformational stages. Cataclastic texture predominantes in polycrystalline and coarser-grained pyrite. Little or no cataclastic texture is observed in single, fine-grained pyrite crystals. Annealing is characterized by recrystallization of pyrite, while fracture filling is characterized by replacement and infilling of cataclastic fractures in pyrite grains by chalcopyrite. Cataclastic deformation texture is likely to have formed at about 400°C to 500°C and at 1 kb to 3 kb pressures, typical of low-grade and/or greenschist-facies metamorphic conditions, whereas annealing textures dominate at temperatures over 500°C-550°C and at 0.69 kb to 1.7 kb pressures, typical of uppergreenschist-/amphibolite-facies metamorphism. Fracture-filling textures, however, should have formed at less than 600°C and less than 500 bars. These temperatures indicate the maximum temperatures that could be reached in such deformation processes. The actual temperatures should be less than these values. The coexistence of at least two or all of the textures in at least one sample from the Küre massive sulfide deposits may indicate that the ore bodies were subjected to a progressive deformation/metamorphic event, ranging from greenschist- to upper greenschist- or even to amphibolite-facies conditions. The imbricate thrust fault and plunging anticlinal/synclinal structures between the Akgöl Formation and the Küre Ophiolite, which postdate the formation of the massive sulfide deposits, may have been the driving mechanism for the development of deformational- and late-deformational textures in the district. Also, it is proposed that many of the copper-bearing minerals may have been remobilized from their original settings to nearby fractures during late deformational stages; this is a possible explanation of why the massive ore tends to be confined to fault planes rather than within altered basalt sequences.
Açıklama
Anahtar Kelimeler
Jeoloji, Yerbilimleri, Ortak Disiplinler
Kaynak
Turkish Journal of Earth Sciences
WoS Q Değeri
Scopus Q Değeri
Q2
Cilt
11
Sayı
3
